A system for ultrasonic computed tomography of attenuation and speed of ultrasound propagation along with simultaneous pulse echo imaging of the same plane has been developed under a three year NSF grant which expires in May, 1979. Use of moderately large, focused transducers has minimized refraction artifacts in attenuation images and provided high resolution in pulse echo and attentuation images of the breast. Use of the small transducer area utilized by others has provided state-of-the-art velocity images. Initial design studies on 18 patients and normal volunteers have allowed development of images with surprising detail and have revealed the complementary relations between ultrasonic attenuation and velocity images. These studies have generated considerable support among clinicians for more extensive clinical trials. Clinical trials of noninvasive breast cancer diagnosis with ultrasonic computed tomography of attenuation and velocity in comparison with pulse echo ultrasound and other imaging modalities are proposed. Approximately 140 patients and 20 normal volunteers will be imaged in the first two years with the basic pulse echo and ultrasonic CT techniques available at the initiation of the project. An additional 80 patients and volunteers will be imaged in the third year with the more quantitative and artifact free techniques developed in the first two years. Most patients will be those in which carcinoma is indicated strongly or in which mammography suggests a small malignant mass. Double blind studies of interpretation of ultrasound, x ray and microwave mammography will be conducted as will extensivehistopathologic correlation. Development of both improved phase dependent and of phase independent imaging of ultrasonic attenuation as well as development of more accurate velocity imaging is proposed. Initial investigationnof reflection techniques both or ultrasonic computed tomography and more qualitative attenuation imaging will be undertaken.